How to properly avoid warning about sh_link not set for section ".ARM.exidx"?

Question

If in my linker script I have this:

.ARM.exidx :
{
    . = ALIGN(4);
    PROVIDE(__exidx_start = .);

    *(.ARM.exidx* .gnu.linkonce.armexidx.*);

    . = ALIGN(4);
    PROVIDE(__exidx_end = .);
} > rom AT > rom

I get following warning when building the project:

/home/freddie/arm-none-eabi-gcc-7.1.0-170503/bin/../lib/gcc/arm-none-eabi/7.1.0/../../../../arm-none-eabi/bin/ld: output/./application.elf: warning: sh_link not set for section `.ARM.exidx'

So I move the symbols "out" of the section:

. = ALIGN(4);
PROVIDE(__exidx_start = .);

.ARM.exidx :
{
    *(.ARM.exidx* .gnu.linkonce.armexidx.*);
} > rom AT > rom

. = ALIGN(4);
PROVIDE(__exidx_end = .);

The warning is gone... What's the difference? Due to the fact that I generate linker script automatically, I would really prefer to have the symbols "in" the section - then there's no difference what memory region (here "flash") was used for previous section.

Interestingly, another "generic" approach suitable for automatic generation gives exactly the same warning:

.ARM.exidx :
{
    *(.ARM.exidx* .gnu.linkonce.armexidx.*);
} > rom AT > rom

PROVIDE(__exidx_start = ADDR(.ARM.exidx));
PROVIDE(__exidx_end = ADDR(.ARM.exidx) + SIZEOF(.ARM.exidx));

score 0 · Answer 1 · answered Mar 03 '20 at 20:33

I fixed the problem by changing:

  .ARM.exidx :
  {
    __exidx_start = .;
    *(.ARM.exidx* .gnu.linkonce.armexidx.*)
    __exidx_end = .;
    . = ALIGN(4);
  } > FLASH

to:

  .ARM :
  {
    __exidx_start = .;
    *(.ARM.exidx* .gnu.linkonce.armexidx.*)
    __exidx_end = .;
    . = ALIGN(4);
  } > FLASH

I think that this works because certain magic output section names set some flags automatically.

How to properly avoid warning about sh_link not set for section ".ARM.exidx"?

1 Answers1